2019/07/25 by Robin Uren, Stephen Beecher, Stephen J. Beecher +3 · 25 citations
Engineering · Mathematics · Physics and Astronomy · #Adaptive optics and wavefront sensing #Algorithm #Beam (structure) #Combinatorics #Computer science #Gaussian beam #Mathematics #Optical Polarization and Ellipsometry #Optics #Orbital Angular Momentum in Optics #Physics #Topology (electrical circuits)
paper · pdf · doi:10.1109/jqe.2019.2931006
published in IEEE Journal of Quantum Electronics 55(5), 1-9 (IEEE Photonics Society)
openalex publication_date 2019/07/25 · openalex created_date 2019/07/30 · openalex updated_date 2026/07/29
Generation of a donut-shaped first-order Laguerre-Gaussian (LG01) vortex mode via a method designed to yield high mode purity is reported. Our approach utilizes a novel twin-spot end-pumping scheme to directly excite the first order Hermite-Gaussian (HG01) mode in a solid-state laser, followed by a novel astigmatic mode converter based on spherical (concave) mirrors aligned at oblique incidence. A simple theoretical model for the mode converter is derived and from this the design approach is explained along with the potential benefits compared with conventional schemes-based cylindrical-lens astigmatic mode converters, particularly for power scaling. As a proof-of-principle and to confirm the benefits of this scheme in terms of high mode purity we have applied it to an end-pumped Nd:YVO4laser to generate a (LG01) beam with a controllable sense of azimuthal phase and hence orbital angular momentum. A method for characterizing the resulting beam-based on analysis of the spiral interference pattern derived with the aid of a Mach-Zehnder interferometer is described and yields a value for the LG01mode purity of 94%. Common sources of mode impurity are identified and the prospects for scaling to higher power whilst maintaining high mode purity are considered.